On 26 February 2014, Japan provided the IAEA with an update on radioactivity in seawater at TEPCO's Fukushima Daiichi Nuclear Power Station (NPS).
The report mentions the water leak reported by TEPCO to the Nuclear Regulation Authority of Japan (NRA) on 15 and 16 February 2014. Two other TEPCO documents provide more information on the leak. They are available here and here. Additionally TEPCO had an issue with the Spent Fuel Pool in Unit 4 and halted the fuel removal process for several hours.
Based on current information presented in this update, the concentrations of all radionuclides (i.e. Cs-134, Cs-137, total Beta and H-3) indicate no significant change before and after the occurrence of the water leakage. The concentration of Cs-134 and Cs-137 at the sampling points T-1 and T-2-1 in the period from 10 December 2013 to 22 February 2014 have remained below the limit values of concentration.
The NRA also provided an update on the sea area monitoring results for radioactivity obtained from sea water samples taken at a distance of two to 200 kilometres from TEPCO's Fukushima Daiichi NPS.